Two patents showing prior art ways of directing coolant fluid into and from a laser mirror are shown in U.S. Pat. No. 3,637,296 and U.S. Pat. No. 3,854,799. Two U.S. Patent applications which show related laser mirrors are U.S. Ser. No. 576,493 filed May 12, 1975 now U.S. Pat. No. 4,006,973 and U.S. Ser. No. 576,492 filed on the same date now U.S. Pat. No. 4,006,972. These applications have a common assignee with subject application.